Spatio-temporal expression analysis of the calcium-binding protein calumenin in the rodent brain

Calumenin is a Ca2+-binding protein that belongs to the CREC superfamily. It contains six EF-hand domains that exhibit a low affinity for Ca2+ as well as an endoplasmic reticulum retention signal. Calumenin exhibits a broad and relatively high expression in various brain regions during development as demonstrated by in situ hybridization. Signal intensity of calumenin is highest during the early development and then declines over time to reach a relatively low expression in adult animals. Immunohistochemistry indicates that at the P0 stage, calumenin expression is most abundant in migrating neurons in the zones around the lateral ventricle. In the brain of adult animals, it is expressed in various glial and neuronal cell types, including immature neurons in subgranular zone of hippocampal dentate gyrus. At the subcellular level, calumenin is identified in punctuate and diffuse distribution mostly in somatic regions where it co-localizes with endoplasmic reticulum (ER) and partially Golgi apparatus. Upon subcellular fractionation, calumenin is enriched in fractions containing membranes and is only weakly present in soluble fractions. This study points to a possible important role of calumenin in migration and differentiation of neurons, and/or in Ca2+ signaling between glial cells and neurons.

▶We analyze the expression of the Ca2+-binding protein calumenin in the rodent brain. ▶Calumenin exhibits higher expression in early developmental stages. ▶Calumenin is expressed by neurons, glia, and progenitor cells. ▶Calumenin co-localizes with the ER and the Golgi complex but not with synaptic sites. ▶Calumenin may play a role in migration, differentiation, and Ca2+ signaling of neurons.